(a) Field of the Invention
This invention relates to filtration materials and absorbent products derived from the combustion of sugar cane residues and methods of manufacturing such products.
(b) Prior Art
In domestic and industrial filtration processes and operations minerals such as diatomaceous earth, diatomite, infursorial earth, tripolite and kieselughr are commonly used as a filter media or filter aid. For example, finely powdered diatomaceous earth is used to precoat the filter elements in swimming pool filters, to aid in the filtration of the water pumped from the pool and returned to the pool after filtering.
The development of new filtration materials has been hampered by economic considerations in that substitute materials for the well-known filtration products must be economically competitive, have a filter cycle at least as good as products now on the market such as diatomaceous earth and have no adverse environmental consequences.
Heretofore, in the process of extracting sugar, when cane stalks are subjected to crushing and other processing in a sugar mill, the cane residues or bagasse (the later term will be exclusively used hereinafter, for convenience) become available in substantial quantities. It has been a problem of the art to find a suitable use for this large volume, low value bagasse by-product material. Such uses have included the manufacture of paper and certain building materials. However, the principal use of bagasse has become the employment of such material as a fuel for the sugar mill boilers. Bagasse (typical analysis is sugar 3%, fibrous material 50%, and water 47%--percentages by weight) which is fed to sugar mill boilers burns to an ash made up of undergrate or furnace ash of low carbon and unburnt or partially burnt fibre content and fly ash which, because it tends to be carried away in the gas stream before combustion is fully completed, can be of significantly higher carbon and fibre content. This resulting boiler ash was generally viewed as a waste product and therefore discarded apart from some restricted use as a soil conditioner and as a rather poor quality lightweight aggregate in the manufacture of concrete and in road construction.